Information recording apparatus and method, and computer program

ABSTRACT

An information recording apparatus ( 2 ) is for forming a record mark corresponding to a recording signal by applying a laser beam to a recording medium, and is provided with: a light source ( 21 ) for emitting the laser beam; and a signal generating device ( 22 ) for generating a recording pulse signal for driving the light source on the basis of the recording signal, the recording pulse signal includes a mark period and a space period, a level of the recording pulse signal corresponds to a recording power by which waveform distortion is greater than or equal to an upper limit (L) or is less than or equal to a lower limit (−L) of an amplitude limit value on a limit equalizer ( 15 ), in the mark period corresponding to a long mark.

TECHNICAL FIELD

The present invention relates to an information recording apparatus andmethod which record data onto a recording medium, and a computer programwhich makes a computer function as the information recording apparatus.

BACKGROUND ART

Into a recordable or rewritable recording medium such as a DVD-R(DVD-Recordable) and a DVD-RW (DVD-Re-writable), data is recorded byirradiating a recording surface of the optical disc with a laser beam.In the portion irradiated with the laser beam on the recording surfaceof the recording medium, a condition of a recording film is changed dueto an increase in temperature, which forms a record mark on therecording surface.

Thus, by modulating the laser beam with a recording pulse having a timewidth corresponding to the data to be recorded and thereby generating alaser pulse with a length corresponding to the data to be recorded, andby applying the generated laser pulse to the recording medium, it ispossible to form the record mark with a length corresponding to the datato be recorded, on the recording medium.

On the other hand, in order to improve an SN ratio of a read signal readfrom the recording medium on which the data is recorded at high density,there is known a technology in which a filtering process for emphasizinghigh frequencies is performed on the read signal, for waveformequalization. In particular, according to a patent document 1, thetechnology is disclosed that the high frequencies can be emphasizedwithout any intersymbol interference by performing the filtering processafter amplitude limit is performed on the read signal (a technologyabout a so-called limit equalizer).

Patent document 1: Japanese Patent No. 3459563

DISCLOSURE OF INVENTION Subject to be Solved by the Invention

Here, waveform distortion could occur in the read signal. The waveformdistortion indicates that there is a discrepancy between a proper signallevel and a signal level that actually appears in the read signalR_(RF). If the waveform distortion is included in a range for theamplitude limit on the limit equalizer (i.e. if coherence is increasedbetween the waveform distortion and an amplitude limit value on thelimit equalizer), the high-frequency emphasis performed after theamplitude limit further emphasizes the waveform distortion. This maylead to such a disadvantage that a record mark with a relatively longrun length is misjudged to be another record mark. Specifically, forexample, it may lead to such a disadvantage that a record mark with arun length of 8T is misjudged to be a combination of a record mark witha run length of 4T, a space with a run length of 2T, and a record markwith a run length of 2T, for example.

In view of the aforementioned problems, it is therefore an object of thepresent invention to provide an information recording apparatus andmethod which can record data on a recording medium and which allowswaveform equalization while performing amplitude limit in a bettermanner.

Means for Solving the Subject

The above object of the present invention can be achieved by a firstinformation recording apparatus for forming a record mark correspondingto a recording signal by applying a laser beam to a recording medium,the information recording apparatus provided with: a light source foremitting the laser beam; and a signal generating device for generating arecording pulse signal for driving the light source on the basis of therecording signal, the recording pulse signal including a mark period inwhich the record mark is formed and a space period in which the recordmark is not formed, a level of the recording pulse signal correspondingto a recording power by which waveform distortion of a read signalobtained by reading the record mark is greater than or equal to an upperlimit or is less than or equal to a lower limit of an amplitude limitvalue on a limit equalizer, which performs high-frequency emphasis onthe read signal, in the mark period corresponding to a long mark.

The above object of the present invention can be also achieved by asecond information recording apparatus for forming a record markcorresponding to a recording signal by applying a laser beam to arecording medium, the information recording apparatus provided with: alight source for emitting the laser beam; and a signal generating devicefor generating a recording pulse signal for driving the light source onthe basis of the recording signal, the recording pulse signal includinga mark period in which the record mark is formed and a space period inwhich the record mark is not formed, a level of the recording pulsesignal corresponding to a recording power by which waveform distortionof a read signal obtained by reading the record mark is greater than orequal to a maximum amplitude or is less than or equal to a minimumamplitude of a read signal obtained by reading the second shortestrecord mark, in the mark period corresponding to a long mark.

The above object of the present invention can be also achieved by athird information recording apparatus for forming a record markcorresponding to a recording signal by applying a laser beam to arecording medium, the information recording apparatus provided with: alight source for emitting the laser beam; and a signal generating devicefor generating a recording pulse signal for driving the light source onthe basis of the recording signal, the recording pulse signal includinga mark period in which the record mark is formed and a space period inwhich the record mark is not formed, a level of the recording pulsesignal corresponding to a recording power by which waveform distortionof a read signal obtained by reading the record mark is greater than orequal to a maximum amplitude or is less than or equal to a minimumamplitude of a read signal obtained by reading the shortest record mark,in the mark period corresponding to a long mark.

The above object of the present invention can be also achieved by afirst information recording method of forming a record markcorresponding to a recording signal by applying a laser beam to arecording medium, the information recording method provided with: asignal generating process of generating a recording pulse signal fordriving a light source on the basis of the recording signal; and anapplying process of applying a laser pulse on the recording medium onthe basis of the recording pulse signal, the recording pulse signalincluding a mark period in which the record mark is formed and a spaceperiod in which the record mark is not formed, a level of the recordingpulse signal corresponding to a recording power by which waveformdistortion of a read signal obtained by reading the record mark isgreater than or equal to an upper limit or is less than or equal to alower limit of an amplitude limit value on a limit equalizer, whichperforms high-frequency emphasis on the read signal, in the mark periodcorresponding to a long mark.

The above object of the present invention can be also achieved by asecond information recording method of forming a record markcorresponding to a recording signal by applying a laser beam to arecording medium, the information recording method provided with: asignal generating process of generating a recording pulse signal fordriving a light source on the basis of the recording signal; and anapplying process of applying a laser pulse on the recording medium onthe basis of the recording pulse signal, the recording pulse signalincluding a mark period in which the record mark is formed and a spaceperiod in which the record mark is not formed, a level of the recordingpulse signal corresponding to a recording power by which waveformdistortion of a read signal obtained by reading the record mark isgreater than or equal to a maximum amplitude or is less than or equal toa minimum amplitude of a read signal obtained by reading the secondshortest record mark, in the mark period corresponding to a long mark.

The above object of the present invention can be also achieved by athird information recording method of forming a record markcorresponding to a recording signal by applying a laser beam to arecording medium, the information recording method provided with: asignal generating device for generating a recording pulse signal fordriving a light source on the basis of the recording signal; and anapplying process of applying a laser pulse on the recording medium onthe basis of the recording pulse signal, the recording pulse signalincluding a mark period in which the record mark is formed and a spaceperiod in which the record mark is not formed, a level of the recordingpulse signal corresponding to a recording power by which waveformdistortion of a read signal obtained by reading the record mark isgreater than or equal to a maximum amplitude or is less than or equal toa minimum amplitude of a read signal obtained by reading the shortestrecord mark, in the mark period corresponding to a long mark.

The above object of the present invention can be also achieved by afirst computer program which is executed by an information recordingapparatus provided with a light source and which is for forming a recordmark corresponding to a recording signal by applying a laser beam to arecording medium, the computer program making the information recordingapparatus perform: a signal generating process of generating a recordingpulse signal for driving a light source on the basis of the recordingsignal; and an applying process of applying a laser pulse on therecording medium on the basis of the recording pulse signal, therecording pulse signal including a mark period in which the record markis formed and a space period in which the record mark is not formed, alevel of the recording pulse signal corresponding to a recording powerby which waveform distortion of a read signal obtained by reading therecord mark is greater than or equal to an upper limit or is less thanor equal to a lower limit of an amplitude limit value on a limitequalizer, which performs high-frequency emphasis on the read signal, inthe mark period corresponding to a long mark.

The above object of the present invention can be also achieved by asecond computer program which is executed by an information recordingapparatus provided with a light source and which is for forming a recordmark corresponding to a recording signal by applying a laser beam to arecording medium, the computer program making the information recordingapparatus perform: a signal generating process of generating a recordingpulse signal for driving a light source on the basis of the recordingsignal; and an applying process of applying a laser pulse on therecording medium on the basis of the recording pulse signal, therecording pulse signal including a mark period in which the record markis formed and a space period in which the record mark is not formed, alevel of the recording pulse signal corresponding to a recording powerby which waveform distortion of a read signal obtained by reading therecord mark is greater than or equal to a maximum amplitude or is lessthan or equal to a minimum amplitude of a read signal obtained byreading the second shortest record mark, in the mark periodcorresponding to a long mark.

The above object of the present invention can be also achieved by athird computer program which is executed by an information recordingapparatus provided with a light source and which is for forming a recordmark corresponding to a recording signal by applying a laser beam to arecording medium, the computer program making the information recordingapparatus perform: a signal generating device for generating a recordingpulse signal for driving a light source on the basis of the recordingsignal; and an applying process of applying a laser pulse on therecording medium on the basis of the recording pulse signal, therecording pulse signal including a mark period in which the record markis formed and a space period in which the record mark is not formed, alevel of the recording pulse signal corresponding to a recording powerby which waveform distortion of a read signal obtained by reading therecord mark is greater than or equal to a maximum amplitude or is lessthan or equal to a minimum amplitude of a read signal obtained byreading the shortest record mark, in the mark period corresponding to along mark.

The operation and other advantages of the present invention will becomemore apparent from embodiments explained below.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view showing a recording pulse waveform (write strategy) inan example.

FIG. 2 is a view conceptually showing the basic structure of aninformation reproducing apparatus provided with a limit equalizer.

FIG. 3 is a block diagram conceptually showing the structure of thelimit equalizer.

FIG. 4 is a waveform chart conceptually showing an operation of settingthe upper limit and the lower limit of an amplitude limit value on asample value series.

FIG. 5 are waveform charts conceptually showing an operation ofobtaining a high-frequency emphasized read sample value series, on thesample value series.

FIG. 6 are waveform charts conceptually showing waveform distortion.

FIG. 7 are waveform charts conceptually showing a relation between thewaveform distortion and the lower limit of the amplitude limit value ona read signal (or sample value series).

FIG. 8 are waveform charts conceptually showing the operation ofobtaining a high-frequency emphasized read sample value series in eachof a case where the waveform distortion is included in the amplitudelimit range (i.e. in a case where a condition A is not satisfied) and acase where the waveform distortion is not included in the amplitudelimit range (i.e. in a case where a condition A is satisfied), on thesample value series that the waveform distortion occurs.

FIG. 9 is a graph showing a change in symbol error rate with respect tothe positional relation between the lower limit of the amplitude limitvalue and the waveform distortion.

FIG. 10 is a waveform chart conceptually showing the relation betweenthe waveform distortion and the lower limit of the amplitude limit valueon the read signal (or sample value series).

FIG. 11 is a waveform chart conceptually showing the relation betweenthe waveform distortion and the lower limit of the amplitude limit valueon the read signal (or sample value series).

FIG. 12 are waveform charts conceptually showing the waveformdistortion.

FIG. 13 is a waveform chart conceptually showing the relation betweenthe waveform distortion and the lower limit of the amplitude limit valueon the read signal (or sample value series).

FIG. 14 is a waveform chart conceptually showing the relation betweenthe waveform distortion and the lower limit of the amplitude limit valueon the read signal (or sample value series).

FIG. 15 is a waveform chart conceptually showing the relation betweenthe waveform distortion and the lower limit of the amplitude limit valueon the read signal (or sample value series).

FIG. 16 is a waveform chart showing an example of the waveform of theread signal obtained by reproducing the recording medium.

FIG. 17 is a view showing another example of the recording pulsewaveform (write strategy) in the example.

FIG. 18 is a view showing another example of the recording pulsewaveform (write strategy) in the example.

FIG. 19 is a waveform chart to explain an asymmetry value.

FIG. 20 is a block diagram schematically showing the entire structure ofan information recording apparatus to which the present invention isapplied.

FIG. 21 is a block diagram showing the inner structures of an opticalpickup and a recording control device.

FIG. 22 is a circuit diagram showing the detailed structure of a LDdriver.

FIG. 23 is a graph showing a relation between a drive current suppliedto a laser diode and an output power of a laser beam emitted from thelaser diode.

FIG. 24 is a flowchart showing a flow of operations of the informationrecording apparatus.

DESCRIPTION OF REFERENCE CODES

-   1 information reproducing apparatus-   2 information recording apparatus-   10, 20 spindle motor-   11, 21 pickup-   12 HPF-   13 A/D converter-   14 pre-equalizer-   15, 25 limit equalizer-   16 binary circuit-   17 decoding circuit-   151 amplitude limit value setting clock-   1516 averaging circuit-   152 amplitude limit block-   1522 interpolation filter-   1523 limiter-   153 high-frequency emphasis block-   22 recording control device

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, as the best mode for carrying out the present invention, anexplanation will be given on embodiments of the information recordingapparatus and method, and the computer program of the present invention.

Embodiments of Information Recording Apparatus

A first embodiment of the information recording apparatus of the presentinvention is an information recording apparatus for forming a recordmark corresponding to a recording signal by applying a laser beam to arecording medium, the information recording apparatus provided with: alight source for emitting the laser beam; and a signal generating devicefor generating a recording pulse signal for driving the light source onthe basis of the recording signal, the recording pulse signal includinga mark period in which the record mark is formed and a space period inwhich the record mark is not formed, a level of the recording pulsesignal corresponding to a recording power by which waveform distortionof a read signal obtained by reading the record mark is greater than orequal to an upper limit or is less than or equal to a lower limit of anamplitude limit value on a limit equalizer, which performshigh-frequency emphasis on the read signal, in the mark periodcorresponding to a long mark.

According to the first embodiment of the information recording apparatusof the present invention, the record mark can be formed on the recordingmedium by applying the laser beam to the recording medium from the lightsource which is driven on the basis of the recording pulse signal. Bythis, the data corresponding to the record signal can be recorded on therecording medium. The recording pulse signal includes the mark period inwhich the record mark is formed and the space period in which the recordmark is not formed.

In the first embodiment, in particular, the level of the recording pulsesignal corresponds to the recording power by which the waveformdistortion of the read signal is greater than or equal to the upperlimit or is less than or equal to the lower limit of the amplitude limitvalue on the limit equalizer, in the mark period corresponding to thelong mark. Thus, in the reproduction of the record mark recorded on thebasis of the recording pulse signal, even if the read signal has thewaveform distortion, the waveform distortion is limited to be greaterthan or equal to the upper limit or to be less than or equal to thelower limit of the amplitude limit value on the limit equalizer. Thus,it is possible to preferably prevent such a disadvantage that thewaveform distortion is further emphasized, which is caused by that thewaveform distortion is included in the range for the amplitude limit onthe limit equalizer. Thus, for example, it is possible to preferablyprevent such a disadvantage that the long mark is misjudged to beanother record mark. By this, it is possible to preferably perform thehigh-frequency emphasis on the read signal, on the limit equalizer.

As described above, according to the information recording apparatus inthe first embodiment, it is possible to record the data which allowswaveform equalization while performing amplitude limit in a bettermanner, onto the recording medium.

A second embodiment of the information recording apparatus of thepresent invention is an information recording apparatus for forming arecord mark corresponding to a recording signal by applying a laser beamto a recording medium, the information recording apparatus providedwith: a light source for emitting the laser beam; and a signalgenerating device for generating a recording pulse signal for drivingthe light source on the basis of the recording signal, the recordingpulse signal including a mark period in which the record mark is formedand a space period in which the record mark is not formed, a level ofthe recording pulse signal corresponding to a recording power by whichwaveform distortion of a read signal obtained by reading the record markis greater than or equal to a maximum amplitude or is less than or equalto a minimum amplitude of a read signal obtained by reading the secondshortest record mark, in the mark period corresponding to a long mark.

According to the second embodiment of the information recordingapparatus of the present invention, as in the information recordingapparatus in the first embodiment, it is possible to form the recordmark on the recording medium.

In the second embodiment, in particular, the level of the recordingpulse signal corresponds to the recording power by which the waveformdistortion of the read signal obtained by reading the record mark isgreater than or equal to the maximum amplitude or is less than or equalto the minimum amplitude of the read signal obtained by reading thesecond shortest record mark (e.g. a record mark with a run length of 4Tif the recording medium is a DVD, and a record mark with a run length of3T if the recording medium is a Blu-ray Disc). Here, in general, theupper limit and the lower limit of the amplitude limit value on thelimit equalizer are set to be less than or equal to the maximumamplitude or to be greater than or equal to the minimum amplitude of theread signal obtained by reading the second shortest record mark. Thus,even if the read signal has the waveform distortion in the reproductionof the record mark recorded on the basis of the recording pulse signal,the waveform distortion is limited to be greater than or equal to theupper limit or to be less than or equal to the lower limit of theamplitude limit value on the limit equalizer. Thus, it is possible topreferably prevent such a disadvantage that the waveform distortion isfurther emphasized, which is caused by that the waveform distortion isincluded in the range for the amplitude limit on the limit equalizer.Thus, for example, it is possible to preferably prevent such adisadvantage that the long mark is misjudged to be another record mark.By this, it is possible to preferably perform the high-frequencyemphasis on the read signal, on the limit equalizer.

As described above, according to the information recording apparatus inthe second embodiment, it is possible to record the data which allowswaveform equalization while performing amplitude limit in a bettermanner, onto the recording medium.

A third embodiment of the information recording apparatus of the presentinvention is an information recording apparatus for forming a recordmark corresponding to a recording signal by applying a laser beam to arecording medium, the information recording apparatus provided with: alight source for emitting the laser beam; and a signal generating devicefor generating a recording pulse signal for driving the light source onthe basis of the recording signal, the recording pulse signal includinga mark period in which the record mark is formed and a space period inwhich the record mark is not formed, a level of the recording pulsesignal corresponding to a recording power by which waveform distortionof a read signal obtained by reading the record mark is greater than orequal to a maximum amplitude or is less than or equal to a minimumamplitude of a read signal obtained by reading the shortest record mark,in the mark period corresponding to a long mark.

According to the third embodiment of the information recording apparatusof the present invention, as in the information recording apparatus inthe first embodiment and the information recording apparatus in thesecond embodiment, it is possible to form the record mark on therecording medium.

In the third embodiment, in particular, the level of the recording pulsesignal corresponds to the recording power by which the waveformdistortion of the read signal obtained by reading the record mark isgreater than or equal to the maximum amplitude or is less than or equalto the minimum amplitude of the read signal obtained by reading theshortest record mark (e.g. a record mark with a run length of 3T if therecording medium is a DVD, and a record mark with a run length of 2T ifthe recording medium is a Blu-ray Disc). Here, in general, the upperlimit and the lower limit of the amplitude limit value on the limitequalizer are set to be greater than or equal to the maximum amplitudeor to be less than or equal to the minimum amplitude of the read signalobtained by reading the shortest record mark, and the upper limit andthe lower limit are set to be less than or equal to the maximumamplitude or is greater than or equal to the minimum amplitude of theread signal obtained by reading the second shortest record mark. Thus,even if the read signal has the waveform distortion in the reproductionof the record mark recorded on the basis of the recording pulse signal,it is possible to increase the possibility that the waveform distortionis limited to be greater than or equal to the upper limit or to be lessthan or equal to the lower limit of the amplitude limit value on thelimit equalizer. Thus, it is possible to appropriately prevent such adisadvantage that the waveform distortion is further emphasized, whichis caused by that the waveform distortion is included in the range forthe amplitude limit on the limit equalizer. Thus, for example, it ispossible to preferably prevent such a disadvantage that the long mark ismisjudged to be another record mark. By this, it is possible topreferably perform the high-frequency emphasis on the read signal, onthe limit equalizer.

As described above, according to the information recording apparatus inthe third embodiment, it is possible to record the data which allowswaveform equalization while performing amplitude limit in a bettermanner, onto the recording medium.

In one aspect of the first, second, or third embodiment of theinformation recording apparatus of the present invention, the level ofthe recording pulse signal corresponds to the recording power by whichreproduction compatibility is ensured, in the mark period correspondingto the long mark.

According to this aspect, it is possible to ensure the reproductioncompatibility in the reproduction of the record mark recorded on thebasis of the recording pulse signal.

In an aspect of the information recording apparatus in which the levelof the recording pulse signal corresponds to the recording power bywhich the reproduction compatibility is ensured in the mark periodcorresponding to the long mark, as described above, the recording powerby which the reproduction compatibility is ensured may be a recordingpower by which degree of modulation is in a predetermined range.

By virtue of such construction, the degree of modulation can be includedin the predetermined range, in the reproduction of the record markrecorded on the basis of the recording pulse signal.

In an aspect of the information recording apparatus in which therecording power by which the reproduction compatibility is ensured isthe recording power by which the degree of modulation is in thepredetermined range, as described above, the recording power by whichthe degree of modulation is in the predetermined range may be arecording power by which the degree of modulation is 40% or more.

By virtue of such construction, the degree of modulation can be set to40% or more, in the reproduction of the record mark recorded on thebasis of the recording pulse signal.

In another aspect of the first, second, or third embodiment of theinformation recording apparatus of the present invention, the level ofthe recording pulse signal corresponds to at least one of a recordingpower and a recording pulse width by which asymmetry is in apredetermined range, in the mark period corresponding to a short mark.

According to this aspect, the asymmetry can be included in thepredetermined range, in the reproduction of the record mark recorded onthe basis of the recording pulse signal.

In an aspect of the information recording apparatus in which the levelof the recording pulse signal corresponds to at least one of therecording power and the recording pulse width by which the asymmetry isin the predetermined range, in the mark period corresponding to theshort mark, as described above, the recording power by which theasymmetry is in the predetermined range may be a recording power bywhich the asymmetry is in a range of −0.10 to 0.15.

By virtue of such construction, the asymmetry can be included in therange of −0.10 to 0.15, in the reproduction of the record mark recordedon the basis of the recording pulse signal.

In another aspect of the first, second, or third embodiment of theinformation recording apparatus of the present invention, the short markcorresponds to the shortest record mark (e.g. a record mark with a runlength of 3T if the recording medium is a DVD, and a record mark with arun length of 2T if the recording medium is a Blu-ray Disc), and thelong mark corresponds to a record mark other than the short mark (e.g.record marks with run lengths of 4T to 11T and 14T if the recordingmedium is a DVD, and record marks with run lengths of 3T to 9T if therecording medium is a Blu-ray Disc).

According to this aspect, it is possible to preferably form the longmark and the short mark as defined above.

In another aspect of the first, second, or third embodiment of theinformation recording apparatus of the present invention, the short markcorresponds to the shortest record mark (e.g. a record mark with a runlength of 3T if the recording medium is a DVD, and a record mark with arun length of 2T if the recording medium is a Blu-ray Disc) and thesecond shortest mark (e.g. a record mark with a run length of 4T if therecording medium is a DVD, and a record mark with a run length of 3T ifthe recording medium is a Blu-ray Disc), and the long mark correspondsto a record mark other than the short mark (e.g. record marks with runlengths of 5T to 11T and 14T if the recording medium is a DVD, andrecord marks with run lengths of 4T to 9T if the recording medium is aBlu-ray Disc) . . . .

According to this aspect, it is possible to preferably form the longmark and the short mark as defined above.

In another aspect of the first, second, or third embodiment of theinformation recording apparatus of the present invention, the short markcorresponds to the record mark by which a signal level is not a maximumamplitude, and the long mark corresponds to the record mark by which thesignal level is the maximum amplitude.

According to this aspect, it is possible to preferably form the longmark and the short mark as defined above.

Embodiments of Information Recording Method

A first embodiment of the information recording method of the presentinvention is an information recording method of forming a record markcorresponding to a recording signal by applying a laser beam to arecording medium, the information recording method provided with: asignal generating process of generating a recording pulse signal fordriving a light source on the basis of the recording signal; and anapplying process of applying a laser pulse on the recording medium onthe basis of the recording pulse signal, the recording pulse signalincluding a mark period in which the record mark is formed and a spaceperiod in which the record mark is not formed, a level of the recordingpulse signal corresponding to a recording power by which waveformdistortion of a read signal obtained by reading the record mark isgreater than or equal to an upper limit or is less than or equal to alower limit of an amplitude limit value on a limit equalizer, whichperforms high-frequency emphasis on the read signal, in the mark periodcorresponding to a long mark.

According to the first embodiment of the information recording method ofthe present invention, it is possible to receive the same variouseffects as those that can be received by the first embodiment of theinformation recording apparatus of the present invention.

Incidentally, in response to the various aspects in the aforementionedfirst embodiment of the information recording apparatus of the presentinvention, the first embodiment of the information recording method ofthe present invention can also adopt various aspects.

A second embodiment of the information recording method of the presentinvention is an information recording method of forming a record markcorresponding to a recording signal by applying a laser beam to arecording medium, the information recording method provided with: asignal generating process of generating a recording pulse signal fordriving a light source on the basis of the recording signal; and anapplying process of applying a laser pulse on the recording medium onthe basis of the recording pulse signal, the recording pulse signalincluding a mark period in which the record mark is formed and a spaceperiod in which the record mark is not formed, a level of the recordingpulse signal corresponding to a recording power by which waveformdistortion of a read signal obtained by reading the record mark isgreater than or equal to a maximum amplitude or is less than or equal toa minimum amplitude of a read signal obtained by reading the secondshortest record mark, in the mark period corresponding to a long mark.

According to the second embodiment of the information recording methodof the present invention, it is possible to receive the same variouseffects as those that can be received by the second embodiment of theinformation recording apparatus of the present invention.

Incidentally, in response to the various aspects in the aforementionedsecond embodiment of the information recording apparatus of the presentinvention, the second embodiment of the information recording method ofthe present invention can also adopt various aspects.

A third embodiment of the information recording method of the presentinvention is an information recording method of forming a record markcorresponding to a recording signal by applying a laser beam to arecording medium, the information recording method provided with: asignal generating device for generating a recording pulse signal fordriving a light source on the basis of the recording signal; and anapplying process of applying a laser pulse on the recording medium onthe basis of the recording pulse signal, the recording pulse signalincluding a mark period in which the record mark is formed and a spaceperiod in which the record mark is not formed, a level of the recordingpulse signal corresponding to a recording power by which waveformdistortion of a read signal obtained by reading the record mark isgreater than or equal to a maximum amplitude or is less than or equal toa minimum amplitude of a read signal obtained by reading the shortestrecord mark, in the mark period corresponding to a long mark.

According to the third embodiment of the information recording method ofthe present invention, it is possible to receive the same variouseffects as those that can be received by the third embodiment of theinformation recording apparatus of the present invention.

Incidentally, in response to the various aspects in the aforementionedthird embodiment of the information recording apparatus of the presentinvention, the third embodiment of the information recording method ofthe present invention can also adopt various aspects.

Embodiments of Computer Program

A first embodiment of the computer program of the present invention is acomputer program which is executed by an information recording apparatusprovided with a light source and which is for forming a record markcorresponding to a recording signal by applying a laser beam to arecording medium, the computer program making the information recordingapparatus perform: a signal generating process of generating a recordingpulse signal for driving a light source on the basis of the recordingsignal; and an applying process of applying a laser pulse on therecording medium on the basis of the recording pulse signal, therecording pulse signal including a mark period in which the record markis formed and a space period in which the record mark is not formed, alevel of the recording pulse signal corresponding to a recording powerby which waveform distortion of a read signal obtained by reading therecord mark is greater than or equal to an upper limit or is less thanor equal to a lower limit of an amplitude limit value on a limitequalizer, which performs high-frequency emphasis on the read signal, inthe mark period corresponding to a long mark.

According to the first embodiment of the computer program of the presentinvention, the aforementioned first embodiment of the informationrecording apparatus of the present invention can be relatively easilyrealized as a computer reads and executes the computer program from aprogram storage device, such as a ROM, a CD-ROM, a DVD-ROM, and a harddisk, or as it executes the computer program after downloading theprogram through a communication device.

Incidentally, in response to the various aspects in the aforementionedfirst embodiment of the information recording apparatus of the presentinvention, the first embodiment of the computer program of the presentinvention can also employ various aspects.

A second embodiment of the computer program of the present invention isa computer program which is executed by an information recordingapparatus provided with a light source and which is for forming a recordmark corresponding to a recording signal by applying a laser beam to arecording medium, the computer program making the information recordingapparatus perform: a signal generating process of generating a recordingpulse signal for driving a light source on the basis of the recordingsignal; and an applying process of applying a laser pulse on therecording medium on the basis of the recording pulse signal, therecording pulse signal including a mark period in which the record markis formed and a space period in which the record mark is not formed, alevel of the recording pulse signal corresponding to a recording powerby which waveform distortion of a read signal obtained by reading therecord mark is greater than or equal to a maximum amplitude or is lessthan or equal to a minimum amplitude of a read signal obtained byreading the second shortest record mark, in the mark periodcorresponding to a long mark.

According to the second embodiment of the computer program of thepresent invention, the aforementioned second embodiment of theinformation recording apparatus of the present invention can berelatively easily realized as a computer reads and executes the computerprogram from a program storage device, such as a ROM, a CD-ROM, aDVD-ROM, and a hard disk, or as it executes the computer program afterdownloading the program through a communication device.

Incidentally, in response to the aforementioned various aspects in thesecond embodiment of the information recording apparatus of the presentinvention, the second embodiment of the computer program of the presentinvention can also employ various aspects.

A third embodiment of the computer program of the present invention is acomputer program which is executed by an information recording apparatusprovided with a light source and which is for forming a record markcorresponding to a recording signal by applying a laser beam to arecording medium, the computer program making the information recordingapparatus perform: a signal generating device for generating a recordingpulse signal for driving a light source on the basis of the recordingsignal; and an applying process of applying a laser pulse on therecording medium on the basis of the recording pulse signal, therecording pulse signal including a mark period in which the record markis formed and a space period in which the record mark is not formed, alevel of the recording pulse signal corresponding to a recording powerby which waveform distortion of a read signal obtained by reading therecord mark is greater than or equal to a maximum amplitude or is lessthan or equal to a minimum amplitude of a read signal obtained byreading the shortest record mark, in the mark period corresponding to along mark.

According to the third embodiment of the computer program of the presentinvention, the aforementioned third embodiment of the informationrecording apparatus of the present invention can be relatively easilyrealized as a computer reads and executes the computer program from aprogram storage device, such as a ROM, a CD-ROM, a DVD-ROM, and a harddisk, or as it executes the computer program after downloading theprogram through a communication device.

Incidentally, in response to the aforementioned various aspects in thethird embodiment of the information recording apparatus of the presentinvention, the third embodiment of the computer program of the presentinvention can also employ various aspects.

The above object of the present invention can be also achieved by afirst embodiment of a computer program product in a computer-readablemedium for tangibly embodying a program of instructions which isexecuted by an information recording apparatus provided with a lightsource and which is for forming a record mark corresponding to arecording signal by applying a laser beam to a recording medium, thecomputer program product making the information recording apparatusperform: a signal generating process of generating a recording pulsesignal for driving a light source on the basis of the recording signal;and an applying process of applying a laser pulse on the recordingmedium on the basis of the recording pulse signal, the recording pulsesignal including a mark period in which the record mark is formed and aspace period in which the record mark is not formed, a level of therecording pulse signal corresponding to a recording power by whichwaveform distortion of a read signal obtained by reading the record markis greater than or equal to an upper limit or is less than or equal to alower limit of an amplitude limit value on a limit equalizer, whichperforms high-frequency emphasis on the read signal, in the mark periodcorresponding to a long mark.

According to the first embodiment of the computer program product of thepresent invention, the aforementioned first embodiment of theinformation recording apparatus of the present invention can be embodiedrelatively readily, by loading the computer program product from arecording medium for storing the computer program product, such as a ROM(Read Only Memory), a CD-ROM (Compact Disc-Read Only Memory), a DVD-ROM(DVD Read Only Memory), a hard disk or the like, into the computer, orby downloading the computer program product, which may be a carrierwave, into the computer via a communication device. More specifically,the computer program product may include computer readable codes tocause the computer (or may comprise computer readable instructions forcausing the computer) to function as the aforementioned first embodimentof the information recording apparatus of the present invention.

Incidentally, in response to the various aspects in the aforementionedfirst embodiment of the information recording apparatus of the presentinvention, the first embodiment of the computer program product of thepresent invention can also employ various aspects.

The above object of the present invention can be also achieved by asecond embodiment of a computer program product in a computer-readablemedium for tangibly embodying a program of instructions which isexecuted by an information recording apparatus provided with a lightsource and which is for forming a record mark corresponding to arecording signal by applying a laser beam to a recording medium, thecomputer program making the information recording apparatus perform: asignal generating process of generating a recording pulse signal fordriving a light source on the basis of the recording signal; and anapplying process of applying a laser pulse on the recording medium onthe basis of the recording pulse signal, the recording pulse signalincluding a mark period in which the record mark is formed and a spaceperiod in which the record mark is not formed, a level of the recordingpulse signal corresponding to a recording power by which waveformdistortion of a read signal obtained by reading the record mark isgreater than or equal to a maximum amplitude or is less than or equal toa minimum amplitude of a read signal obtained by reading the secondshortest record mark, in the mark period corresponding to a long mark.

According to the second embodiment of the computer program product ofthe present invention, the aforementioned second embodiment of theinformation recording apparatus of the present invention can be embodiedrelatively readily, by loading the computer program product from arecording medium for storing the computer program product, such as a ROM(Read Only Memory), a CD-ROM (Compact Disc-Read Only Memory), a DVD-ROM(DVD Read Only Memory), a hard disk or the like, into the computer, orby downloading the computer program product, which may be a carrierwave, into the computer via a communication device. More specifically,the computer program product may include computer readable codes tocause the computer (or may comprise computer readable instructions forcausing the computer) to function as the aforementioned secondembodiment of the information recording apparatus of the presentinvention.

Incidentally, in response to the various aspects in the aforementionedsecond embodiment of the information recording apparatus of the presentinvention, the second embodiment of the computer program product of thepresent invention can also employ various aspects.

The above object of the present invention can be also achieved by athird embodiment of a computer program product in a computer-readablemedium for tangibly embodying a program of instructions which isexecuted by an information recording apparatus provided with a lightsource and which is for forming a record mark corresponding to arecording signal by applying a laser beam to a recording medium, thecomputer program making the information recording apparatus perform: asignal generating device for generating a recording pulse signal fordriving a light source on the basis of the recording signal; and anapplying process of applying a laser pulse on the recording medium onthe basis of the recording pulse signal, the recording pulse signalincluding a mark period in which the record mark is formed and a spaceperiod in which the record mark is not formed, a level of the recordingpulse signal corresponding to a recording power by which waveformdistortion of a read signal obtained by reading the record mark isgreater than or equal to a maximum amplitude or is less than or equal toa minimum amplitude of a read signal obtained by reading the shortestrecord mark, in the mark period corresponding to a long mark.

According to the third embodiment of the computer program product of thepresent invention, the aforementioned third embodiment of theinformation recording apparatus of the present invention can be embodiedrelatively readily, by loading the computer program product from arecording medium for storing the computer program product, such as a ROM(Read Only Memory), a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM(DVD Read Only Memory), a hard disk or the like, into the computer, orby downloading the computer program product, which may be a carrierwave, into the computer via a communication device. More specifically,the computer program product may include computer readable codes tocause the computer (or may comprise computer readable instructions forcausing the computer) to function as the aforementioned third embodimentof the information recording apparatus of the present invention.

Incidentally, in response to the various aspects in the aforementionedthird embodiment of the information recording apparatus of the presentinvention, the third embodiment of the computer program product of thepresent invention can also employ various aspects.

The operation and other advantages of the present invention will becomemore apparent from the example explained below.

As explained above, according to the first embodiment of the informationrecording apparatus and method, and the computer program of the presentinvention, the level of the recording pulse signal corresponds to therecording power by which the waveform distortion is greater than orequal to the upper limit or is less than or equal to the lower limit ofthe amplitude limit value on the limit equalizer, in the mark periodcorresponding to the long mark. According to the second embodiment ofthe information recording apparatus and method, and the computer programof the present invention, the level of the recording pulse signalcorresponds to the recording power by which the waveform distortion isgreater than or equal to the maximum amplitude or is less than or equalto the minimum amplitude of the read signal obtained by reading thesecond shortest record mark, in the mark period corresponding to thelong mark. According to the third embodiment of the informationrecording apparatus and method, and the computer program of the presentinvention, the level of the recording pulse signal corresponds to therecording power by which the waveform distortion is greater than orequal to the maximum amplitude or is less than or equal to the minimumamplitude of the read signal obtained by reading the shortest recordmark, in the mark period corresponding to the long mark. Therefore, itis possible to record the data which allows waveform equalization whileperforming amplitude limit in a better manner, onto the recordingmedium.

Example

The present invention is characterized in that it separately sets arecording power for a long mark and a recording power for a short mark,on an information recording apparatus which records information bydriving a laser beam source with a recording pulse signal. Hereinafter,its example will be described on the basis of the drawings.

FIG. 1 shows a recording pulse waveform (write strategy) in the example.In FIG. 1, data is formed by a mark period Twd with a lengthcorresponding to a data length, and a space period Tsp with a lengthcorresponding to the data length. Incidentally, the length of the spaceperiod is a matter of no importance in the present invention, so thatone portion of the space period is omitted in the drawing.

In a Blu-ray Disc of the optical disc, which is one specific example ofthe recording medium, marks with a length of 2T and a length of 3T areformed by a recording pulse waveform that includes a single pulse, andmarks with a length of 4T or more are formed by a recording pulsewaveform of a substantially concave type, which includes a top pulse 60tp, a last pulse 60 lp, and a middle pulse 60 m. Specifically, as shownin the upper part in FIG. 1, in the Blu-ray Disc, the 2T and 3Trecording pulse waveforms have a period for a space power Ps, a periodfor a peak power Po, and a period for a cooling power Pcl. Moreover, the4T or more recording pulse waveforms have the period for the space powerPs, the top pulse period 60 tp for the peak power Po, the last pulseperiod 60 lp for the peak power Po, the period 60 m for a middle powerPm, and the period for the cooling power Pcl.

Incidentally, in this specification, the “recording power” conceptuallyincludes the peak power and the middle power. In other words, as for therecording pulse waveform, in the case of the 2T and 3T marks in FIG. 1,the recording power is only the peak power; however, in the case of the4T or more marks, the recording power indicates the peak power and themiddle power.

Incidentally, in the DVD of the optical disc, which is one specificexample of the recording medium, the marks with a length of 3T and alength of 4T are formed by the recording pulse waveform that includes asingle pulse, and marks with a length of 5T or more are formed by arecording pulse waveform of a substantially concave type, which includesthe top pulse 60 tp, the last pulse 60 lp, and the middle pulse 60 m.

Next, an explanation will be given on a method of determining arecording power for the short mark and the long mark. In the example,the recording power is determined in view of the degree of modulation;asymmetry; and a relation between the waveform distortion which occursin a read signal and the upper limit or lower limit of an amplitudelimit value on a limit equalizer, which performs waveform equalizationon the read signal obtained by reading the data, or the like, as arecording status evaluation parameter.

Hereinafter, the limit equalizer and the waveform distortion will bedescribed before the method of determining the recording power.

Firstly, with reference to FIG. 2 to FIG. 5, the structure and operationprinciple of the limit equalizer will be described. For convenience ofexplanation, the structure and operation principle of an informationreproducing apparatus provided with the limit equalizer will bedescribed.

FIG. 2 conceptually shows the basic structure of the informationreproducing apparatus provided with the limit equalizer. As shown inFIG. 2, an information reproducing apparatus 1 is provided with aspindle motor 10, a pickup (PU) 11, a HPF (High Pass Filter) 12, an A/Dconverter 13, a pre-equalizer 14, a limit equalizer 15, a binary circuit16, and a decoding circuit 17.

The pickup 11 photoelectrically converts reflected light when a laserbeam LB is applied to a recording surface of an optical disc 100 rotatedby the spindle motor 10, to thereby generate a read signal R_(RF).

The HPF 12 removes a low-frequency component of the read signal R_(RF)outputted from the pickup, and it outputs a resulting read signal R_(HC)to the A/D converter 13.

The A/D converter 13 samples the read signal in accordance with asampling clock outputted from a PLL (Phased Lock Loop) not illustratedor the like, and it outputs a resulting read sample value series RS tothe pre-equalizer 14.

The pre-equalizer 14 removes intersymbol interference based ontransmission characteristics in an information reading system, which isformed of the pickup 11 and the optical disc 100, and it outputs aresulting read sample value series RS_(C) to the limit equalizer 15.

The limit equalizer 15 performs a high-frequency emphasis process on theread sample value series RS_(C) without increasing the intersymbolinterference, and it outputs a resulting high-frequency emphasized readsample value series RS_(H) to the binary circuit 16.

The binary circuit 16 performs a binary process on the high-frequencyemphasized read sample value series RS_(H), and it outputs a resulting abinary signal to the decoding circuit 17.

The decoding circuit 17 performs a decoding process on the binarysignal, and it outputs a resulting reproduction signal to externalreproduction equipment such as a display and a speaker. As a result, thedata recorded on the optical disc 100 (e.g. video data, audio data, andthe like) is reproduced.

Next, with reference to FIG. 3, the more detailed structure of the limitequalizer 15 will be described. FIG. 3 is a block diagram conceptuallyshowing the structure of the limit equalizer 15. As shown in FIG. 3, thelimit equalizer 15 is provided with an amplitude limit value settingblock 151, an amplitude limit block 152, and a high-frequency emphasisblock 153.

The amplitude limit value setting block 151 sets the upper limit and thelower limit of the amplitude limit value used on the amplitude limitblock 152, on the basis of the read sample value series RS_(C). Theamplitude limit block 152 performs an amplitude limit process on theread sample value series RS_(C), on the basis of the upper limit and thelower limit of the amplitude limit value set on the amplitude limitvalue setting block 151. A sample value series RS_(LIM) through theamplitude limit process is outputted to the high-frequency emphasisblock 153. The high-frequency emphasis block 153 performs a filteringprocess for emphasizing high frequencies, on the sample value seriesRS_(LIM) through the amplitude limit process. As a result, thehigh-frequency emphasized read sample value series RS_(H) is obtained.

More specifically, a reference sample timing detection circuit 1511detects reference sample timing on the basis of the read sample valueseries RS_(C). The detected reference sample timing is outputted to asample hold circuit 1514 through a delayer 1512 for providing aone-clock delay and an OR circuit 1513. On the sample hold circuit 1514,a sample value series RS_(P) outputted from an interpolation filter 1522is sampled and held in accordance with the reference sample timingoutputted through the delayer 1512 and the OR circuit 1513

Incidentally, the interpolation filter 1522 performs an interpolationprocess on the read sample value series RS_(C), to thereby generate aninterpolated sample value series which is obtained when the read signalR_(RF) read from the optical disc 100 is sampled in the middle timing ofthe clock timing by the sampling clock used on the A/D converter 14. Thegenerated interpolated sample value series is included in the readsample value series RS_(C) and is outputted to the limiter 1523 and thesample hold circuit 1514 as the sample value series RS_(P).

from the sample value series RS_(P) sampled and held, a reference levelRf is reduced on a subtracter 1515, wherein Rf=0 if a zero level is usedas the reference level Rf. The subtraction result is outputted to anaveraging circuit 1516. The averaging circuit 1516 calculates an averagevalue of sample values. The calculated average value of sample values isset as the upper limit and the lower limit of the amplitude limit value.Specifically, a value obtained by adding the average value to thereference level is set as the upper limit of the amplitude limit value,and a value obtained by subtracting the average value from the referencelevel is set as the lower limit of the amplitude limit value. If thezero level is used as the reference level, a value obtained by providinga positive sign for the calculated average value of sample values is setas the upper limit of the amplitude limit value, and a value obtained byproviding a negative sign for the calculated average value of samplevalues is set as the lower limit of the amplitude limit value. In thefollowing explanation, for convenience of explanation, the zero level isused as the reference level Rf.

Specifically, with reference to FIG. 4, an explanation will be given onthe upper limit and the lower limit of the amplitude limit value set onthe amplitude limit value setting block 151. FIG. 4 is a waveform chartconceptually showing an operation of setting the upper limit and thelower limit of the amplitude limit value on the sample value seriesRS_(C).

FIG. 4 shows the read signals R_(RF) obtained by reading data withrelatively short run lengths (specifically, data with run lengths of 2T,3T, and 4T if the optical disc 100 is a Blu-ray Disc) of the read signaland its sample value series RS_(C). As shown in FIG. 4, an average valueL of interpolated sample values (sample values generated on theinterpolation filter 1522) located before a zero cross point (i.e.before in terms of time) and interpolated sample values located afterthe zero cross point (i.e. after in terms of time) is set as theabsolute value of the upper value and the lower value of the amplitudelimit value. In other words, the upper limit of the amplitude limitvalue is set as L, and the lower limit of the amplitude limit value isset as −L.

In FIG. 3 again, the limiter 1523 performs amplitude limit on the samplevalue series RS_(P) on the basis of the upper limit and the lower limitset on the amplitude limit value setting block 151. Specifically, if asample value included in the sample value series RS_(P) is less than theupper limit L and greater than the lower limit −L, the sample value isoutputted as the sample value series RS_(LIM) as it is. On the one hand,if a sample value included in the sample value series RS_(P) is greaterthan or equal to the upper limit L, the upper limit L is outputted asthe sample value series RS_(LIM). On the other hand, if a sample valueincluded in the sample value series RS_(P) is less than or equal to theupper limit −L, the lower limit −L is outputted as the sample valueseries RS_(LIM).

The high-frequency emphasis block 153 increases the signal level of onlythe sample value series RS_(LIM) corresponding to data with the shortestrun length (e.g. the data with a run length of 3T if the optical disc100 is a DVD, and the data with a run length of 2T if the optical disc100 is a Blu-ray Disc) in the sample value series RS_(LIM).

Specifically, the sample value series RS_(LIM) inputted to thehigh-frequency emphasis block 153 is inputted to coefficient multipliers1535 and 1538 having a multiplier coefficient of −k and coefficientmultipliers 1536 and 1537 having a multiplier coefficient of k, as it isor through delayers 1532, 1533, and 1534 for providing a one-clockdelay. The outputs of the coefficient multipliers 1535, 1536, 1537, and1538 are added on an adder 1539. A high-frequency read sample valueseries RS_(HIG) which is an addition result is added to the read samplevalue series R_(C) which is inputted to the adder 1531 through thedelayer 1530 for providing a three-clock delay, on the adder 1531. As aresult, the high-frequency emphasized read sample value series RS_(H) isobtained.

Now, with reference to FIG. 5, an operation of obtaining thehigh-frequency emphasized read sample value series RS_(H) will bedescribed in more detail. FIG. 5 are waveform charts conceptuallyshowing the operation of obtaining the high-frequency emphasized readsample value series RS_(H), on the sample value series RS_(C).

As shown in FIG. 5( a), the high-frequency read sample value seriesRS_(HIG) outputted from the adder 1531 is calculated on the basis of thesample values at respective time points D (−1.5), D(−0.5), D(0.5), andD(1.5) in the sample value series RS_(LIM). Specifically, if the samplevalues at the respective time points D (−1.5), D(−0.5), D(0.5), andD(1.5) in the sample value series RS_(LIM) are set to Sip(−1), Sip(0),Sip(1), and Sip(2), then,RS_(HIG)=(−k)×Sip(−1)+k×Sip(0)+k×Sip(1)+(−k)×Sip(2).

At this time, as shown in FIG. 5( b), the sample values Sip(−1) andSip(0) at the time points D(−1.5) and D(−0.5) corresponding to the datawith a run length of 2T are substantially equal to each other. Moreover,the sample values Sip(1) and Sip(2) at the time points D(0.5) and D(1.5)corresponding to the data with a run length of 2T are substantiallyequal to each other.

Moreover, as shown in FIG. 5( c), the sample values Sip(−1) and Sip(0)at the time points D(−1.5) and D(−0.5) corresponding to the data witheach of run lengths of 3T and 4T are both the upper limit L of theamplitude limit value, due to the amplitude limit by the amplitude limitblock 152. In the same manner, the sample values Sip(1) and Sip(2) atthe time points D(0.5) and D(115) corresponding to the data with each ofrun lengths of 3T and 4T are both the lower limit −L of the amplitudelimit value, due to the amplitude limit by the amplitude limit block152. In other words, the dispersion of the sample values before andafter the reference sample point is forcibly controlled.

Thus, even if the value of the coefficient k is increased on thecoefficient multipliers 1535, 1536, 1537, and 1538 in order to increasethe high-frequency emphasis, the high-frequency read sample value seriesRS_(HIG) obtained at the zero cross point D(0) is kept constant.Therefore, the intersymbol interference does not occur. As describedabove, according to the information reproducing apparatus 1 providedwith the limit equalizer 15, the dispersion of the sample values beforeand after the zero cross point in the read signal, which causes theintersymbol interference, is forcibly controlled in the high-frequencyemphasis. Thus, even if the sufficient high-frequency emphasis isperformed on the high-frequency emphasis block 153, the intersymbolinterference does not occur.

Next, with reference to FIG. 6, the waveform distortion will bedescribed. FIG. 6 are waveform charts conceptually showing the waveformdistortion.

As shown in FIG. 6( a), the waveform distortion indicates a differencebetween a proper signal level and a signal level that actually appearsin the read signal R_(RF). The waveform distortion is quantitativelydefined by a waveform distortion amount D with respect to the maximumamplitude A of the read signal R_(RF), and a waveform distortion amountD′ which is a signal level from the zero level to the peak of thewaveform distortion. In FIG. 6( a), a thick dashed line indicates theproper signal level when there is no waveform distortion. If there is nowaveform distortion, the waveform distortion amount D is obviously zero.

Incidentally, the waveform distortion shown in FIG. 6( a) indicates thewaveform distortion that the signal level in a middle portion ischanged, compared to the signal level in a front edge portion and a rearedge portion of the read signal R_(RF). Apart from such waveformdistortion, there can be the waveform distortion that the signal levelin the front edge portion and the middle portion is changed, compared tothe signal level in the rear edge portion of the read signal R_(RF) asshown in FIG. 6( b); and the waveform distortion that the signal levelin the middle edge portion and the rear portion is changed, compared tothe signal level in the front edge portion of the read signal R_(RF) asshown in FIG. 6( c). For any waveform distortion, the structure andoperation described later can be obviously adopted.

Moreover, in the example, it is preferable to focus on the waveformdistortion which occurs in the read signal corresponding to the recordmark with a relatively long run length (e.g. data with a run length of11T if the optical disc 100 is a DVD, and data with a run length of 8Tif the optical disc 100 is a Blu-ray Disc). Alternatively, in view ofimportance for synchronization data (i.e. sync data), it is preferableto focus on the waveform distortion which occurs in the read signalcorresponding to the record mark corresponding to the synchronizationdata (e.g. data with a run length of 14T if the optical disc 100 is aDVD, and data with a run length 9T if the optical disc 100 is a Blu-rayDisc).

Next, an explanation will be given on a method of determining arecording power for the short mark (specifically, the record marks withrun lengths of 2T and 3T if the optical disc 100 is a Blu-ray Disc, andthe record marks with run lengths of 3T and 4T if the optical disc 100is a DVD) and the long mark (specifically, the record marks with runlengths of 4T to 9T if the optical disc 100 is a Blu-ray Disc, and therecord marks with run lengths of 5T to 11T, and 14T if the optical disc100 is a DVD). Firstly, the recording power for the long mark will bedescribed. In the example, the recording power for the long mark isdetermined by the following three conditions listed:

(Condition A) the waveform distortion (specifically, the waveformdistortion amount D′) is less than or equal to the lower limit −L of theamplitude limit value of the limit equalizer 15;

(Condition B) the waveform distortion (specifically, the waveformdistortion amount D′) is less than or equal to the minimum amplitude ofthe read signal corresponding to a record mark with the second shortestrun length (specifically, the record mark with a run length of 3T if theoptical disc 100 is a Blu-ray Disc, and the record mark with a runlength of 4T if the optical disc 100 is a DVD); and

(Condition C) the waveform distortion (specifically, the waveformdistortion amount D′) is less than or equal to the minimum amplitude ofthe read signal corresponding to a record mark with the shortest runlength (specifically, the record mark with a run length of 2T if theoptical disc 100 is a Blu-ray Disc, and the record mark with a runlength of 3T if the optical disc 100 is a DVD).

Firstly, with reference to FIG. 7, the condition A will be described.FIG. 7 are waveform charts conceptually showing a relation between thewaveform distortion and the lower limit −L of the amplitude limit valueon the read signal R_(RF) (or sample value series).

As shown in FIG. 7, the recording power is determined to satisfy thecondition A that the waveform distortion is less than or equal to thelower limit −L of the amplitude limit value of the limit equalizer 15.In other words, the recording power is determined such that the waveformdistortion is not included in the amplitude limit range (−L to L) of thelimit equalizer 15.

As described above, by forming the long mark with the recording powerwhich satisfies the condition A, the waveform distortion which can occurin the read signal R_(RF) when the long mark is read is no longerincluded in the amplitude limit range (−L to L) of the limit equalizer15, as shown in FIG. 7. Therefore, it is possible to form the long markwhich preferably allows the high-frequency emphasis on the limitequalizer 15 while eliminating an influence by the waveform distortion.

The effect that the influence by the waveform distortion is eliminatedwill be described with reference to FIG. 8 and FIG. 9. FIG. 8 is awaveform chart conceptually showing the operation of obtaining ahigh-frequency emphasized read sample value series RS_(H) in each of acase where the waveform distortion is included in the amplitude limitrange (i.e. in a case where the condition A is not satisfied) and a casewhere the waveform distortion is not included in the amplitude limitrange (i.e. in a case where a condition A is satisfied), on the samplevalue series RS_(C) that the waveform distortion occurs. FIG. 9 is agraph showing a change in symbol error rate with respect to thepositional relation between the lower limit −L of the amplitude limitvalue and the waveform distortion.

As shown in FIG. 8( a), it is assumed that the waveform distortion has asignal level that is greater than the lower limit −L of the amplitudelimit value. In other words, it is assumed that the long mark is formedwith the recording power that does not satisfy the condition A. In thiscase, the high-frequency emphasized read sample value series RS_(H)outputted from the high-frequency emphasis block 153 is a sum of thehigh-frequency emphasized read sample value series RS_(HIG) and S(0),and as described above,RS_(HIG)=(−k)×Sip(−1)+k×Sip(0)+k×Sip(1)+(−k)×Sip(2). Here, Sip(−1) andSip(2) are limited by a lower limit L2, soRS_(H)=S(0)+k×(−2×L2+Sip(0)+Sip(1)). This increases the value of thehigh-frequency emphasized read sample value series RS_(H), by the valueobtained by multiplying the sum of the lower limit L2, Sip (0), andSip(1) by K. This is not preferable because it emphasizes the waveformdistortion which is originally not to occur. Moreover, due to theemphasized waveform distortion, for example, it may lead to such adisadvantage that the record mark with a relatively long run length ismisjudged to be another record mark, in an information reproducingapparatus that applies PRML.

On the other hand, as shown in FIG. 8( b), it is assumed that thewaveform distortion has a signal level that is less than or equal to thelower limit −L of the amplitude limit value. In other words, it isassumed that the long mark is formed with the recording power thatsatisfies the condition A. In this case, since Sip(−1), Sip(0), Sip(1),and Sip(2) are limited by the lower limit L2, RS_(H)=S(0). Thus, it ispossible to prevent the disadvantage of the emphasized waveformdistortion.

As described above, the effect by the long mark being formed with therecording power that satisfies the condition A is also seen from achange in symbol error rate with respect to the positional relationbetween the lower limit −L of the amplitude limit value and the waveformdistortion. As shown in FIG. 9, compared to the case where the waveformdistortion has the signal level that is greater than the lower limit −Lof the amplitude limit value (i.e. if −L+the waveform distortion amountD′ is negative), the value of SER is improved in the case where thewaveform distortion has the signal level that is less than or equal tothe lower limit −L of the amplitude limit value (i.e. if −L+the waveformdistortion amount D′ is positive).

Next, with reference to FIG. 10, the condition B will be described. FIG.10 is a waveform chart conceptually showing the relation between thewaveform distortion and the lower limit −L of the amplitude limit valueon the read signal R_(RF) (or sample value series).

As shown in FIG. 10, the recording power is determined to satisfy thecondition B that the waveform distortion is less than or equal to asignal level with the minimum amplitude of the read signal correspondingto the record mark with the second shortest run length.

By forming the long mark with the recording power that satisfies thecondition B in this manner, the waveform distortion which can occur inthe read signal R_(RF) when the long mark is read is no longer includedin the amplitude limit range (−L to L) of the limit equalizer 15, asshown in FIG. 10. This is because, in general, the lower limit −L of theamplitude limit value is less than or equal to the minimum amplitude ofthe read signal corresponding to the record mark with the shortest runlength and because the lower limit is greater than or equal to theminimum amplitude of the read signal corresponding to the record markwith the second shortest run length. Therefore, even if the recordingpower is determined to satisfy the condition B, as in the case where therecording power is determined to satisfy the condition A, it is possibleto form the mark which preferably allows the high-frequency emphasis onthe limit equalizer 15 while eliminating the influence by the waveformdistortion.

Next, with reference to FIG. 11, the condition C will be described. FIG.11 is a waveform chart conceptually showing the relation between thewaveform distortion and the lower limit −L of the amplitude limit valueon the read signal R_(RF) (or sample value series).

As shown in FIG. 11, the recording power is determined to satisfy thecondition C that the waveform distortion is less than or equal to asignal level with the minimum amplitude of the read signal correspondingto a record mark with the shortest run length.

By forming the long mark with the recording power that satisfies thecondition C in this manner, the waveform distortion which can occur inthe read signal R_(RF) when the long mark is read is highly possibly notincluded in the amplitude limit range (−L to L) of the limit equalizer15, as shown in FIG. 11. This is because, in general, the lower limit −Lof the amplitude limit value is less than or equal to the minimumamplitude of the read signal corresponding to the record mark with theshortest run length and because the lower limit is greater than or equalto the minimum amplitude of the read signal corresponding to the recordmark with the second shortest run length. Therefore, even if therecording power is determined to satisfy the condition C, it is possibleto form the mark which allows the high-frequency emphasis on the limitequalizer 15 while eliminating the influence by the waveform distortionto some extent which is less than in the case where the recording poweris determined to satisfy the condition A and the condition B.

Incidentally, in the aforementioned explanation, an explanation wasgiven on the operation aimed at the optical disc 100 in which thereflectance of the laser beam LB is reduced by forming the record mark.In other words, an explanation was given on the operation aimed at thecase where the waveform distortion occurs such that the signal levelunintentionally increases in the signal level with the zero level orless. As shown in FIG. 12( a), however, the operation may be aimed atthe optical disc 100 in which the reflectance of the laser beam LB isincreased by recording that data. In other words, it may be aimed at thecase where the waveform distortion occurs such that the signal levelunintentionally reduces in the signal level with the zero level or more.Incidentally, even in the case where the waveform distortion occurs suchthat the signal level unintentionally reduces, there can be the waveformdistortion in which the signal level has changed in the front edgeportion and the middle portion, compared to the signal level in the rearedge portion of the read signal R_(RF), as shown in FIG. 12( b); and thewaveform distortion in which the signal level has changed in the middleportion and the rear edge portion, compared to the signal level in thefront edge portion of the read signal R_(RF), as shown in FIG. 12( c),as in the case where the waveform distortion occurs such that the signallevel unintentionally reduces as shown in FIG. 6( b), in the signallevel with the zero level or more.

An explanation will be given on a method of determining the record powerif it is aimed at the optical disc 100 in which the reflectance of thelaser beam LB is increased by recording the data. In this case, therecording power for the long mark is determined in the following threeconditions listed:

(Condition D) the waveform distortion (specifically, the waveformdistortion amount D′) is greater than or equal to the upper limit L ofthe amplitude limit value of the limit equalizer 15;

(Condition E) the waveform distortion (specifically, the waveformdistortion amount D′) is greater than or equal to the maximum amplitudeof the read signal corresponding to the record mark with the secondshortest run length (specifically, the record mark with a run length of3T if the optical disc 100 is a Blu-ray Disc, and the record mark with arun length of 4T if the optical disc 100 is a DVD); and

(Condition F) the waveform distortion (specifically, the waveformdistortion amount D′) is greater than or equal to the maximum amplitudeof the read signal corresponding to the record mark with the shortestrun length (specifically, the record mark with a run length of 2T if theoptical disc 100 is a Blu-ray Disc, and the record mark with a runlength of 3T if the optical disc 100 is a DVD).

Firstly, with reference to FIG. 13, the condition D will be described.FIG. 13 is a waveform chart conceptually showing the relation betweenthe waveform distortion and the upper limit L of the amplitude limitvalue on the read signal R_(RF) (or sample value series).

As shown in FIG. 13, the recording power is determined to satisfy thecondition D that the waveform distortion is greater than or equal to theupper limit L of the amplitude limit value of the limit equalizer 15. Inother words, the recording power is determined such that the waveformdistortion is no longer included in the amplitude limit range (−L to L)of the equalizer 15.

As described above, by forming the long mark with the recording powerthat satisfies the condition D, the waveform distortion which can occurin the read signal R_(RF) when the long mark is read is no longerincluded in the amplitude limit range (−L to L) of the limit equalizer15, as shown in FIG. 13. Therefore, it is possible to form the long markwhich preferably allows the high-frequency emphasis on the limitequalizer 15 while eliminating the influence by the waveform distortion.

Next, with reference to FIG. 14, the condition E will be described. FIG.14 is a waveform chart conceptually showing the relation between thewaveform distortion and the upper limit L of the amplitude limit valueon the read signal R_(RF) (or sample value series).

As shown in FIG. 14, the recording power is determined to satisfy thecondition E that the waveform distortion is greater than or equal to asignal level with the maximum amplitude of the read signal correspondingto the record mark with the second shortest run length.

By forming the long mark with the recording power that satisfies thecondition E in this manner, the waveform distortion which can occur inthe read signal R_(RF) when the long mark is read is no longer includedin the amplitude limit range (−L to L) of the limit equalizer 15, asshown in FIG. 14. This is because, in general, the upper limit L of theamplitude limit value is greater than or equal to the maximum amplitudeof the read signal corresponding to the record mark with the shortestrun length and because the upper limit is less than or equal to theminimum amplitude of the read signal corresponding to the record markwith the second shortest run length. Therefore, even if the recordingpower is determined to satisfy the condition E, as in the case where therecording power is determined to satisfy the condition D, it is possibleto form the mark which preferably allows the high-frequency emphasis onthe limit equalizer 15 while eliminating the influence by the waveformdistortion.

Next, with reference to FIG. 15, the condition F will be described. FIG.15 is a waveform chart conceptually showing the relation between thewaveform distortion and the upper limit L of the amplitude limit valueon the read signal R_(RF) (or sample value series).

As shown in FIG. 15, the recording power is determined to satisfy thecondition F that the waveform distortion is greater than or equal to asignal level with the maximum amplitude of the read signal correspondingto the record mark with the shortest run length.

By forming the long mark with the recording power that satisfies thecondition F in this manner, the waveform distortion which can occur inthe read signal R_(RF) when the long mark is read is highly possibly notincluded in the amplitude limit range (−L to L) of the limit equalizer15, as shown in FIG. 11. This is because, in general, the upper limit Lof the amplitude limit value is greater than or equal to the maximumamplitude of the read signal corresponding to the record mark with theshortest run length and because the upper limit is less than or equal tothe maximum amplitude of the read signal corresponding to the recordmark with the second shortest run length. Therefore, even if therecording power is determined to satisfy the condition F, it is possibleto form the mark which allows the high-frequency emphasis on the limitequalizer 15 while eliminating the influence by the waveform distortionto some extent which is less than in the case where the recording poweris determined to satisfy the condition D and the condition E.

Incidentally, the recording power for the long mark may be constructedto satisfy the following condition G, in addition to satisfying at leastone of the conditions A to F described above:

(Condition G) the degree of modulation is 40% or more.

The “degree of modulation” is a ratio of the amplitude of the readsignal R_(RF) obtained by reading the data recorded on the recordingmedium to a difference between the zero level and the peak level of theread signal R_(RF). FIG. 16 shows an example of the waveform of the readsignal R_(RF) obtained by reproducing the recording medium. In otherwords, the degree of modulation is a ratio of the amplitude ImaxH−ImaxLof the read signal R_(RF) to the difference Imax H between the zerolevel and the peak level, and it is given by the following equation.

Degree of modulation=(ImaxH−ImaxL)/ImaxH

In general, if the record mark is insufficiently formed with respect tothe recording medium, the degree of modulation reduces and an influenceby noise increases in the reproduction signal. Thus, an S/N ratioreduces, and reproduction compatibility has an adverse effect.Incidentally, “having reproduction compatibility” indicates that therecording medium recorded by a certain information recording apparatuscan be properly reproduced by another information reproducing apparatus.

On the other hand, although it depends on recording conditions and therecording medium, if the degree of modulation is assumed to increasewith an increase of the recording power, the increase is saturated witha certain degree of recording power.

However, as the degree of modulation increases, there is a higherpossibility that it has an adverse effect on a LPP error rate and AR ina DVD-R, an ADIP error rate in a DVD+R, and the like. The AR is an indexindicating an aperture ratio of a LPP detection waveform in a DVD-R andwhether or not LPP is correctly detected. The LPP error rate indicatesan error rate for a LPP signal in the reproduction RF signal. Asdescribed above, in order to ensure the reproduction compatibility, thedegree of modulation is preferably 60% or more. However, the excessivedegree of modulation increases the width of pits formed on the groove onthe recording medium and causes the LPP formed adjacent to the groove tobe unreadable in some cases. This deteriorates the AR and the LPP errorrate. Moreover, in a DVD+R, the excessive degree of modulation increasesthe size of the formed pits and causes pre-addresses pre-recorded on thedisc to be unreadable. This deteriorates the ADIP error rate.

Moreover, the high degree of modulation increases a thermal influence onanother adjacent mark, in particular, on the short mark, and thermalinterference or the like deteriorates recording features. Moreover,since the amount of change in the degree of modulation reduces withrespect to the change in the recording power, a detection accuracyreduces if the degree of modulation is used for detection or the like,such as ROPC (Running Optimum Power Control).

Moreover, if the degree of modulation increases, the waveform distortionalso increases in accordance with the increase.

As described above, the excessive degree of modulation causes variousdisadvantages. Thus, the degree of modulation is desirably reduced asmuch as possible in the range that keeps the reproduction compatibility,for example, to be about “0.4” (40%). Moreover, from the viewpoint ofprevention of the aforementioned various disadvantages, the upper limitof the degree of modulation is desirably about “0.8” (80%). From theabove, the peak power P_(on) of the long mark is desirably in the rangethat the reproduction compatibility is kept; specifically, the degree ofmodulation is a value in a range of about 0.4 to 0.8, and particularly,the degree of modulation is desirably about 0.4.

Next, a method of determining the recording power for the short markwill be described. In the example, the method of determining therecording power for the short mark is a method that satisfies thefollowing condition a:

(Condition a) asymmetry is in a standard range.

Specifically, if the optical disc 100 is a Blu-ray Disc, the condition acorresponds to that the recording power is determined to make theasymmetry be in a range of −0.10 to 0.15. If the optical disc 100 is aDVD, the condition a corresponds to that the recording power isdetermined to make the asymmetry be in a range of −0.05 to 0.15.Incidentally, in addition to or instead of determining the recordingpower for the short mark, a pulse width for the short mark may bedetermined to satisfy such a condition b that the asymmetry is in astandard range.

Moreover, in the recording pulse waveform explained using FIG. 1, therecording power for the long mark and the recording power for the shortmark are set to the same peak power Po. However, the recording power forthe long mark and the recording power for the short mark may be set todifferent peak powers. Specifically, FIG. 17 shows another example ofthe recording pulse. As shown in a recording pulse #1 in FIG. 17, a peakpower Po1 of the recording pulse corresponding to the mark with a lengthof 2T and a peak power Po2 of the recording pulse corresponding to themark with a length other than 2T may have different values. In thiscase, the peak power Po1 of the recording pulse corresponding to themark with a length of 2T may be set variable, and the peak power Po2 ofthe recording pulse corresponding to the mark with a length other than2T may be set variable. Alternatively, the recording power for the shortmark may be also constructed to have a plurality of types of peakpowers. Specifically, as shown in a recording pulse #2 in FIG. 17, thepeak power Po1 of the recording pulse corresponding to the mark with alength of 2T, a peak power Po2 of the recording pulse corresponding tothe mark with a length of 3T, and a peak power Po3 of the recordingpulse corresponding to the mark with a length other than 2T and 3T mayhave different values. In this case, the peak power Po1 of the recordingpulse corresponding to the mark with a length of 2T may be set variable,and the peak power Po2 of the recording pulse corresponding to the markwith a length of 3T may be set variable, and the peak power Po3 of therecording pulse corresponding to the mark with a length other than 2Tand 3T may be set variable.

Alternatively, a pulse width for the recording pulse with the long markand a pulse width for the recording pulse with the short mark may havedifferent pulse widths. Specifically, FIG. 18 shows another example ofthe recording pulse. As shown in a recording pulse #1 in FIG. 18, apulse width for the recording pulse corresponding to the mark with alength of 2T may be set variable. As shown in a recording pulse #2 inFIG. 18, a pulse width for the recording pulse corresponding to the markwith a length of 2T and a pulse width for the recording pulsecorresponding to the mark with a length of 3T may be set variable.

Incidentally, the asymmetry will be described for reference. FIG. 19 isa waveform chart to explain an asymmetry value. As shown in FIG. 19, theasymmetry value indicates a shift or deviation of the amplitude centerof the read signal corresponding to the data with the shortest runlength, with respect to the amplitude center of the read signal R_(RF)corresponding to the data with the longest run length. Specifically, theasymmetry value Asy=((ImaxH+ImaxL)−(IminH+IminL))/(2×(ImaxH−ImaxL)),wherein the amplitude center of the read signal R_(RF) corresponding tothe data with the longest run length is ImaxCnt, ImaxH is the magnitudeof the top amplitude of the read signal R_(RF) corresponding to the datawith the longest run length based on ImaxCnt, ImaxL is the magnitude ofthe bottom amplitude of the read signal R_(RF) corresponding to the datawith the longest run length based on ImaxCnt, IminH is the magnitude ofthe top amplitude of the read signal R_(RF) corresponding to the datawith the shortest run length based on ImaxCnt, and IminL is themagnitude of the bottom amplitude of the read signal R_(RF)corresponding to the data with the shortest run length based on ImaxCnt.Incidentally, ImaxCnt is an average value of the top amplitude value andthe bottom amplitude value of the read signal R_(RF) corresponding tothe data with the longest run length.

Incidentally, in the aforementioned explanation, the record mark withthe shortest run length and the record mark with the second shortest runlength are set to the short marks, and the other record marks are set tothe long marks; however, only the record mark with the shortest runlength may be set as the short mark, and the other record marks may beset as the long marks. Alternatively, the record mark in which theamplitude of the read signal is not the maximum amplitude (specifically,the record marks with run lengths of 3T and 4T if the optical disc 100is a DVD, and the record marks with run lengths of 2T to 4T is theoptical disc 100 is a Blu-ray Disc) may be set as the short mark, andthe record mark in which the amplitude of the read signal is the maximumamplitude (specifically, the record marks with run lengths of 5T to 11Tand 14T if the optical disc 100 is a DVD, and the record marks with runlengths of 5T to 9T is the optical disc 100 is a Blu-ray Disc) may beset as the long mark.

Next, FIG. 20 schematically shows the entire structure of an informationrecording apparatus to which the present invention is applied. Aninformation recording apparatus 2 is an apparatus for recording dataonto the optical disc 100. As the optical disc 100, it is possible touse various optical discs, including a DVD, a Blu-ray Disc, or the like,as described above.

The information recording apparatus 2 is provided with an optical pickup21 for applying the laser beam LB to the optical disc 100; a spindlemotor 20 for controlling the rotation of the optical disc 100; and aservo control device 23 for performing various servo control, includingspindle servo for controlling the rotation of the spindle motor 20, andfocus servo and tracking servo which are relative positional control ofthe optical pickup 21 with respect to the optical disc 100.

The recording control device 22 receives a recording signal, generates adrive signal SD for driving a laser diode inside the optical pickup 21by a process described later, and supplies it to the optical pickup 21.

The servo control device 23 receives the read signal R_(RF) from theoptical pickup 2 and supplies a servo signal S1, such as a trackingerror signal and a focus signal, to the optical pickup 2 on the basis ofthe read signal R_(RF), and supplies a spindle servo signal S2 to thespindle motor 20. By this, various servo processes, such as trackingservo, focus servo, and spindle servo, are performed.

FIG. 21 shows the inner structures of the recording control device 22and the optical pickup 21. As shown in FIG. 21, the optical pickup 21 isprovided with a laser diode 211 for generating the laser beam LB torecord the data onto the optical disc 100; and a front monitor diode(FMD) 212 for receiving the laser beam LB emitted from the laser diode211 and outputting a laser power level signal LD_(out) corresponding tothe laser beam LB.

On the one hand, the recording control device 22 is provided with alaser diode (LD) driver 221; an APC (Automatic Power Control) circuit222; a sample hold (S/H) circuit 223; and a controller 224.

The LD driver 221 supplies an electric current corresponding to therecording signal to the laser diode 211 and records information onto anoptical disc D. The front monitor diode 212 is disposed in the vicinityof the laser diode 211 inside the optical pickup 21, receives the laserbeam LB emitted from the laser diode 211, and outputs the laser powerlevel signal LD_(out) which indicates the level of the laser beam LB.

The sample hold circuit 223 samples and holds the level of the laserpower level signal LD_(out) in timing defined by a sample hold signalAPC-S/H. The APC circuit 222 performs power control on the LD driver 221such that the space power Ps of the laser beam LB emitted from the laserdiode 211 is constant, on the basis of an output signal of the samplehold circuit 223.

The controller 224 mainly performs a recording operation and an APCoperation. Firstly, the recording operation will be described. In therecording operation, the controller 224 generates switch-over signalsSW_(R), SW_(W1), SW_(W2), and SW_(W3) for controlling the amount of anelectric current supplied to the laser diode 221, and it supplies themto the LD driver 221.

FIG. 22 shows the detailed structure of the LD driver 221. As shown inFIG. 22, the LD driver 221 is provided with a cooling-level currentsource 2211, write-level current sources 2212 and 2213, a space-levelcurrent source 2214, and switches 2215, 2216, 2217, and 2218.

The cooling-level current source 2211 is a current source for applying adrive current I_(R) to make the laser diode 211 emit the laser beam LBwith the cooling power Pcl. The drive current I_(R) is supplied to thelaser diode 211 through the switch 2215. Thus, if the switch 2215 isturned on, the drive current I_(R) with the cooling power Pcl issupplied to the laser diode 211, and if switch 2215 is turned off, thesupply of the drive current I_(R) is stopped.

The write-level current sources 2212 and 2213 are current sources forapplying drive currents I_(W1) and I_(W2) to make the laser diode 211emit the laser beam LB with the write power. The drive current I_(W1) issupplied to the laser diode 211 through the switch 2216, and the drivecurrent I_(W2) is supplied to the laser diode 211 through the switch2217.

The space-level current source 2214 is a current source for applying adrive current I_(W3) to make the laser diode 211 emit the laser beam LBwith the space power Ps. The drive current I_(W3) is supplied to thelaser diode 211 through the switch 2218.

In the write strategy by the present invention, the first write power(peak power) Po, the second write power (middle power) Pm which is lowerthan the first write power, and the space power Ps are used (refer toFIG. 1 and the like). If the switch 2218 is turned in the condition thatthe switch 2215 is already turned on, the laser diode 211 is suppliedwith a total drive current of the drive currents I_(R) and I_(W3). Bythis, the laser diode 211 is driven with the space power Ps. Moreover,if the switch 2217 is further turned on in the condition that theswitches 2215 and 2218 are already turned on, the laser diode 211 isfurther supplied with the drive current I_(W2). As a result, a totaldrive current of the drive currents I_(R), I_(W3), and I_(W2) is appliedto the laser diode 211, and the laser diode 211 is driven with thesecond write power Pm. Moreover, if the switch 2216 is further turned onin the condition that the switches 2215, 2217, and 2218 are alreadyturned on, the laser diode 211 is further supplied with the drivecurrent I_(W1). As a result, a total drive current of the drive currentsI_(R), I_(W3), I_(W2), and I_(W1) is applied to the laser diode 211, andthe laser diode 211 is driven with the first write power Po. The supplyof the drive current I_(W1) is stopped if the switch 2216 is turned off.The supply of the drive current I_(W2) is stopped if the switch 2217 isturned off. The supply of the drive current I_(W3) is stopped if theswitch 2218 is turned off.

FIG. 23 shows a relation between the drive current supplied to the laserdiode 211 and the output power of the laser beam emitted from the laserdiode 211. As can be seen from FIG. 23, if the laser diode 211 issupplied with the drive current I_(R), the laser beam LB is emitted withthe cooling power Pcl. If the drive current I_(W3) is further applied inthat condition, the laser beam is emitted with the space power Ps. Ifthe drive current I_(W2) is further applied in that condition, the laserbeam is emitted with the second write power Pm. Moreover, if the drivecurrent I_(W1) is further applied in that condition, the laser beam isemitted with the first write power Po.

In recording the data onto the optical disc 100, basically, the laserbeam LB is emitted with the cooling power Pcl while the drive currentI_(R) is always supplied. Moreover, by adding the drive currents I_(W1)and I_(W2) in accordance with the recording pulse, the first write powerPo or the second write power Pm is applied. By this, the data isrecorded onto the optical disc 100.

Next, the APC operation will be described. The APC operation adjusts thelevel of the drive current supplied to the laser diode 211 from the LDdriver 221 such that the level of the space power Ps of the laser beamLB outputted from the laser diode 211 is constant. More specifically,the drive signal SD from the recording control device 10 is adjustedsuch that the level of the space power Ps is constant, in the long spaceperiod (e.g. 5T to 11T, and 14T space periods) of the space portion ofthe recording signal (on which 8-16 modulation is performed, and whichhas the mark period and the space period with lengths of 3T to 11T and14T).

Specifically, the operation is performed as follows. The controller 224generates the recording pulse corresponding to the recording signal asdescribed above, drives the LD driver 221 by using the recording pulse,and makes the laser diode 211 emit the laser beam LB.

The front monitor diode 212 is disposed in vicinity of the laser diode211 inside the optical pickup 21, receives the laser beam LB emittedfrom the laser diode 211, generates the laser power level signalLD_(out) which indicates the level of the laser beam LB, and supplies itto the sample hold circuit 223.

The sample hold circuit 223 samples the laser power level signalLD_(out) supplied from the front monitor diode 212 in timing provided bythe sample hold signal APC-S/H inputted from the controller 224, and itholds the level for a predetermined period. The sample hold signalAPC-S/H outputted from the controller 224 is a pulse which indicates aperiod to perform APC (referred to as an “APC period”).

Thus, the sample hold circuit 223 holds the level of the laser powerlevel signal LD_(out) in the APC period in the space period of therecording signal, and it supplies the level of the laser power levelsignal LD_(out) to the APC circuit 22. The APC circuit 22 supplies acontrol signal S_(APC) to the LD driver 221 such that the level of thelaser power level signal LD_(out) in the APC period is constant.

The control signal S_(APC) is inputted to the space-level current source2214 in the LD driver 221. By this, in accordance with the controlsignal S_(APC), the electric current I_(W3) applied from the space-levelcurrent source 2214 is changed. In other words, the APC is performedsuch that the level of the space power obtained from the laser diode 211is constant.

Next, a flow of the operations of the aforementioned informationrecording apparatus 2 will be described. A recording process describedlater is performed mainly by the controller 224 shown in FIG. 21controlling the LD driver 221 or the like on the basis of the recordingsignal supplied from the exterior. FIG. 24 is a flowchart showing a flowof operations of the information recording apparatus 2. Incidentally,the controller 224 can perform the recording process by executing aprepared program corresponding to the process described below.

As shown in FIG. 24, firstly, when receiving the recording signalincluding the record data (step S101), the controller 224 determines therecording power that satisfies at least one of the condition A,condition B, condition C, condition D, condition E, and condition F(step S102). At this time, the recording power may be determined thatsatisfies both the condition G and at least one of the condition A,condition B, condition C, condition D, condition E, and condition F.Then, the controller 224 determines the recording power that satisfiesthe condition a and the pulse width that satisfies the condition b (step103).

Then, the controller 224 supplies the LD driver 221 with the controlsignal corresponding to the recording power and the pulse widthdetermined in the step S102 and the step S103. The LD driver 221 drivesthe laser diode 21 on the basis of the supplied control signal andrecords the record mark corresponding to the record data onto theoptical disc 100 (step S104). In this manner, the inputted recordingsignal is recorded onto the optical disc 100.

In particular, if the long mark is formed, the information recordingapparatus 2 outputs the laser beam LB with the recording power thatsatisfies the aforementioned condition A, condition B, condition C,condition D, condition E, or condition F (and moreover, the conditionG). Moreover, if the short mark is formed, it outputs the laser beam LBwith the recording power that satisfies the aforementioned condition A.Therefore, the aforementioned various effects can be preferablyreceived.

Incidentally, in the aforementioned example, the present invention isapplied to a DVD (more specifically, a DVD-R/RW, DVD+R/RW) and a Blu-rayDisc; however, the present invention can be also applied to a HD DVD,DVD-RAM, and the like, in the same manner.

The present invention is not limited to the aforementioned example, butvarious changes may be made, if desired, without departing from theessence or spirit of the invention which can be read from the claims andthe entire specification. An information recording apparatus and method,and a computer program, all of which involve such changes, are alsointended to be within the technical scope of the present invention.

1. An information recording apparatus for forming a record markcorresponding to a recording signal by applying a laser beam to arecording medium, said information recording apparatus comprising: alight source for emitting the laser beam; and a signal generating devicefor generating a recording pulse signal for driving said light source onthe basis of the recording signal, the recording pulse signal includinga mark period in which the record mark is formed and a space period inwhich the record mark is not formed, a level of the recording pulsesignal corresponding to a recording power by which waveform distortionof a read signal obtained by reading the record mark is greater than orequal to an upper limit or is less than or equal to a lower limit of anamplitude limit value on a limit equalizer, which performshigh-frequency emphasis on the read signal, in the mark periodcorresponding to a long mark.
 2. An information recording apparatus forforming a record mark corresponding to a recording signal by applying alaser beam to a recording medium, said information recording apparatuscomprising: a light source for emitting the laser beam; and a signalgenerating device for generating a recording pulse signal for drivingsaid light source on the basis of the recording signal, the recordingpulse signal including a mark period in which the record mark is formedand a space period in which the record mark is not formed, a level ofthe recording pulse signal corresponding to a recording power by whichwaveform distortion of a read signal obtained by reading the record markis greater than or equal to a maximum amplitude or is less than or equalto a minimum amplitude of a read signal obtained by reading the secondshortest record mark, in the mark period corresponding to a long mark.3. An information recording apparatus for forming a record markcorresponding to a recording signal by applying a laser beam to arecording medium, said information recording apparatus comprising: alight source for emitting the laser beam; and a signal generating devicefor generating a recording pulse signal for driving said light source onthe basis of the recording signal, the recording pulse signal includinga mark period in which the record mark is formed and a space period inwhich the record mark is not formed, a level of the recording pulsesignal corresponding to a recording power by which waveform distortionof a read signal obtained by reading the record mark is greater than orequal to a maximum amplitude or is less than or equal to a minimumamplitude of a read signal obtained by reading the shortest record mark,in the mark period corresponding to a long mark.
 4. The informationrecording apparatus according to claim 1, wherein the level of therecording pulse signal corresponds to the recording power by whichreproduction compatibility is ensured, in the mark period correspondingto the long mark.
 5. The information recording apparatus according toclaim 4, wherein the recording power by which the reproductioncompatibility is ensured is a recording power by which degree ofmodulation is in a predetermined range.
 6. The information recordingapparatus according to claim 5, wherein the recording power by which thedegree of modulation is in the predetermined range is a recording powerby which the degree of modulation is 40% or more.
 7. The informationrecording apparatus according to claim 5, wherein the level of therecording pulse signal corresponds to at least one of a recording powerand a recording pulse width by which asymmetry is in a predeterminedrange, in the mark period corresponding to a short mark.
 8. Theinformation recording apparatus according to claim 7, wherein therecording power by which the asymmetry is in the predetermined range isa recording power by which the asymmetry is in a range of −0.10 to 0.15.9. The information recording apparatus according to claim 7, wherein theshort mark corresponds to the shortest record mark, and the long markcorresponds to the record mark other than the short mark.
 10. Theinformation recording apparatus according to claim 7, wherein the shortmark corresponds to the shortest record mark and the second shortestmark, and the long mark corresponds to the record mark other than theshort mark.
 11. The information recording apparatus according to claim7, wherein the short mark corresponds to the record mark by which asignal level is not a maximum amplitude, and the long mark correspondsto the record mark by which the signal level is the maximum amplitude.12. An information recording method of forming a record markcorresponding to a recording signal by applying a laser beam to arecording medium, said information recording method comprising: a signalgenerating process of generating a recording pulse signal for driving alight source on the basis of the recording signal; and an applyingprocess of applying a laser pulse on the recording medium on the basisof the recording pulse signal, the recording pulse signal including amark period in which the record mark is formed and a space period inwhich the record mark is not formed, a level of the recording pulsesignal corresponding to a recording power by which waveform distortionof a read signal obtained by reading the record mark is greater than orequal to an upper limit or is less than or equal to a lower limit of anamplitude limit value on a limit equalizer, which performshigh-frequency emphasis on the read signal, in the mark periodcorresponding to a long mark.
 13. An information recording method offorming a record mark corresponding to a recording signal by applying alaser beam to a recording medium, said information recording methodcomprising: a signal generating process of generating a recording pulsesignal for driving a light source on the basis of the recording signal;and an applying process of applying a laser pulse on the recordingmedium on the basis of the recording pulse signal, the recording pulsesignal including a mark period in which the record mark is formed and aspace period in which the record mark is not formed, a level of therecording pulse signal corresponding to a recording power by whichwaveform distortion of a read signal obtained by reading the record markis greater than or equal to a maximum amplitude or is less than or equalto a minimum amplitude of a read signal obtained by reading the secondshortest record mark, in the mark period corresponding to a long mark.14. An information recording method of forming a record markcorresponding to a recording signal by applying a laser beam to arecording medium, said information recording method comprising: a signalgenerating device for generating a recording pulse signal for driving alight source on the basis of the recording signal; and an applyingprocess of applying a laser pulse on the recording medium on the basisof the recording pulse signal, the recording pulse signal including amark period in which the record mark is formed and a space period inwhich the record mark is not formed, a level of the recording pulsesignal corresponding to a recording power by which waveform distortionof a read signal obtained by reading the record mark is greater than orequal to a maximum amplitude or is less than or equal to a minimumamplitude of a read signal obtained by reading the shortest record mark,in the mark period corresponding to a long mark.
 15. A computer readablerecording medium recording thereon a computer program which is executedby an information recording apparatus comprising a light source andwhich is for forming a record mark corresponding to a recording signalby applying a laser beam to a recording medium, said computer programmaking said information recording apparatus perform: a signal generatingprocess of generating a recording pulse signal for driving a lightsource on the basis of the recording signal; and an applying process ofapplying a laser pulse on the recording medium on the basis of therecording pulse signal, the recording pulse signal including a markperiod in which the record mark is formed and a space period in whichthe record mark is not formed, a level of the recording pulse signalcorresponding to a recording power by which waveform distortion of aread signal obtained by reading the record mark is greater than or equalto an upper limit or is less than or equal to a lower limit of anamplitude limit value on a limit equalizer, which performshigh-frequency emphasis on the read signal, in the mark periodcorresponding to a long mark.
 16. A computer readable recording mediumrecording thereon a computer program which is executed by an informationrecording apparatus comprising a light source and which is for forming arecord mark corresponding to a recording signal by applying a laser beamto a recording medium, said computer program making said informationrecording apparatus perform: a signal generating process of generating arecording pulse signal for driving a light source on the basis of therecording signal; and an applying process of applying a laser pulse onthe recording medium on the basis of the recording pulse signal, therecording pulse signal including a mark period in which the record markis formed and a space period in which the record mark is not formed, alevel of the recording pulse signal corresponding to a recording powerby which waveform distortion of a read signal obtained by reading therecord mark is greater than or equal to a maximum amplitude or is lessthan or equal to a minimum amplitude of a read signal obtained byreading the second shortest record mark, in the mark periodcorresponding to a long mark.
 17. A computer readable recording mediumrecording thereon a computer program which is executed by an informationrecording apparatus comprising a light source and which is for forming arecord mark corresponding to a recording signal by applying a laser beamto a recording medium, said computer program making said informationrecording apparatus perform: a signal generating device for generating arecording pulse signal for driving a light source on the basis of therecording signal; and an applying process of applying a laser pulse onthe recording medium on the basis of the recording pulse signal, therecording pulse signal including a mark period in which the record markis formed and a space period in which the record mark is not formed, alevel of the recording pulse signal corresponding to a recording powerby which waveform distortion of a read signal obtained by reading therecord mark is greater than or equal to a maximum amplitude or is lessthan or equal to a minimum amplitude of a read signal obtained byreading the shortest record mark, in the mark period corresponding to along mark.